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Strongly Confined Deposition of Microwave Energy in Biological Tissue
Dr. Victor Granatstein
Professor, Electrical and Computer Engineering, Univ. of Maryland
October 26, 2007, 2:00 p.m.
Jeong H. Kim Engineering Building, Rm. 1110
ABSTRACT: Two phenomena which might spatially confine the deposition of microwave energy in biological tissue are
1. Sharp focusing of microwave energy to a spot in the near field of a monopole antenna
2. The short absorption length of microwave energy in biological tissue because of relatively high values of relative permittivity, εr, and conductivity, σ
Phenomena #1 has been exploited to make a microwave drill in which 2.4 GHz microwaves are used to make holes in ceramics with diameter of only a few millimeters.
Phenomena #2 has been exploited to make a non-lethal weapon in which pain (but no permanent injury) is induced by 94 GHz microwaves which penetrate only to the nerve layer in the skin.
We have studied exploiting both of these phenomena for microwave hyperthermia of small tumors with minimal irradiation of the surrounding healthy tissue. A miniature semi-rigid coaxial cable would be inserted into the channel made by a hypodermic needle; alternatively, the cable could be inside a hollow needle or inside a catheter inserted with the aid of a needle. The center conductor is extended beyond the end of the co-axial cable to form a small monopole antenna. The power absorption volume is visualized by using the simulation code HFSS for both human muscle and human breast fat, and for frequencies of f = 9, 16, 23 and 30 GHz, and for antenna lengths of h = 0.9 and h = 2.5 mm. For h = 0.9 mm and f= 9 GHz, a spherical absorption region with diameter~ 1.5 mm is predicted. This has been confirmed experimentally by using chicken breast which has electrical properties similar to human muscle (εr 40, σ 10 S/m). Simulations indicate that smaller absorption volumes would be achievable in human muscle by increasing the microwave frequency in the range 9 to 30 GHz; the same cannot be said for human breast fat tissue which has much smaller vales of both εr and σ compared with muscle tissue. Finally we note that the absorption region in the tissue extends beyond the tip of the antenna, so that tumor cells can be destroyed without having to penetrate the tumor with the antenna wire which might result in mestastasis of the malignancy.
BIOGRAPHY: Victor L. Granatstein grew up in Toronto, Canada. He received the Ph. D. degree in electrical engineering from Columbia University, New York in 1963. He was a research scientist at Bell Telephone Laboratories from 1964 to 1972. In 1969-70, he was a Visiting Senior Lecturer at the Hebrew University of Jerusalem. In 1972, he joined the Naval Research Laboratory (NRL) as a Research Physicist, and from 1978 to 1983, he served as Head of NRL's High Power Electromagnetic Radiation Branch. From August 1983 to the present, he has been a Professor in the Electrical and Computer Engineering Department of the University of Maryland, College Park. From 1987 to 1998, he was Director of the Institute for Plasma Research (now renamed Institute for Research in Electronics and Applied Physics) at the University of Maryland. He spent semesters in both 1994 and 2003 as a Visiting Professor at Tel Aviv University. In 2004, he was made Sackler Professor by Special Appointment at Tel Aviv University. His present research interests include electromagnetic radiation from relativistic electron beams, advanced concepts in millimeter wave tubes, the effects of high power microwaves on electronic circuits and systems and microwave hyperthermia of tumors He has co-authored more than 250 research papers in scientific journals and has co-edited three books. He holds a number of patents on active and passive microwave devices. His textbook “Physical Principles of Wireless Communications” will be available in late 2007. Dr. Granatstein is a Fellow of the American Physical Society and a Life Fellow of the IEEE. He has received a number of major research awards including the E.O. Hulbert Annual Science Award (1979), the Superior Civilian Service Award (1980), the Captain Robert Dexter Conrad Award for scientific achievement (awarded by the Secretary of the Navy, 1981), the IEEE Plasma Science and Applications Award (1991) and the Robert L. Woods Award for Excellence in Electronics Technology (1998).
Faculty Host: Reza Ghodssi
This Event is For: Public • Clark School